Alternative placement of thermal sensors on bipolar electrode

ABSTRACT

A medical device for tissue ablation may include a catheter shaft, an expandable member disposed on or coupled to the catheter shaft, and a plurality of elongate electrode assemblies each constructed as a flexible circuit. The expandable member may be configured to shift between an unexpanded configuration and an expanded configuration.The plurality of electrode assemblies may be disposed on an outer surface of the expandable member. Each of the plurality of electrode assemblies may include a temperature sensor aligned with two or more electrodes.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of U.S. patent application Ser. No. 15/874,223,filed Jan. 18, 2018, which is a continuation of application of U.S.application Ser. No. 14,611,755, filed Feb. 2, 2015, now granted as U.S.Pat. No. 9,907,609, which claims priority under 35 U.S.C. § 119 to U.S.Provisional Application Ser. No. 61/935,685, filed Feb. 4, 2014, thedisclosures of which are herein incorporated herein by reference intheir entirety for all purposes.

TECHNICAL FIELD

The present disclosure pertains to medical devices, and methods formanufacturing medical devices. More particularly, the present disclosurepertains to medical devices for tissue ablation.

BACKGROUND

A wide variety of intracorporeal medical devices have been developed formedical use, for example, intravascular use. Some of these devicesinclude guidewires, catheters, and the like. These devices aremanufactured by any one of a variety of different manufacturing methodsand may be used according to any one of a variety of methods. Of theknown medical devices and methods, each has certain advantages anddisadvantages. There is an ongoing need to provide alternative medicaldevices as well as alternative methods for manufacturing and usingmedical devices.

BRIEF SUMMARY

A medical device for tissue ablation may include a catheter shaft, anexpandable balloon disposed on the catheter shaft, where the balloon maybe capable of shifting between an unexpanded configuration and anexpanded configuration. The medical device may include a plurality ofelongate electrode assemblies each constructed as a flexible circuit,the plurality of electrode assemblies may each include a plurality ofelectrodes in at least first and second spaced apart arrays, theplurality of electrode assemblies may be disposed on an outer surface ofthe balloon. Each of the plurality of electrode assemblies may includeone or more temperature sensor aligned with two or more electrodeswithin an array.

A medical device for tissue ablation may include a catheter shaft, anexpandable member coupled to the catheter shaft, and a plurality ofelongate electrode assemblies each constructed as a flexible circuit.The expandable member may be capable of shifting between an unexpandedconfiguration and an expanded configuration. The plurality of electrodeassemblies may be disposed on an outer surface of the expandable member,and each of the plurality of electrode assemblies may include at leastone temperature sensor positioned under at least one electrode.

A medical device for tissue ablation within a body passageway mayinclude a catheter shaft having a longitudinal axis, an expandablemember coupled to the catheter shaft, and a plurality of elongateelectrode assemblies each constructed as a flexible circuit. Theexpandable member may be capable of shifting between an unexpandedconfiguration and an expanded configuration, and the plurality ofelectrode assemblies may be bonded to an outer surface of the expandablemember. Each of the plurality of electrode assemblies may include aplurality of active electrodes, a plurality of ground electrodes, andone or more temperature sensor. The temperature sensor may be linearlyaligned with the plurality of ground electrodes.

The above summary of some embodiments is not intended to describe eachdisclosed embodiment or every implementation of the present disclosure.The Figures, and Detailed Description, which follow, more particularlyexemplify these embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure may be more completely understood in consideration of thefollowing detailed description in connection with the accompanyingdrawings, in which:

FIG. 1 is a schematic view of an example tissue ablation device;

FIGS. 2A, 2B, and 3 are partial top views of prior art electrodeassemblies;

FIG. 4 is a partial top view of an exemplary electrode assembly;

FIG. 5 is a partial top view of an exemplary electrode assembly;

FIGS. 6A and 6B are top views of exemplary electrode assemblies;

FIG. 7 is a perspective view of an exemplary expandable member of atissue ablation device;

FIG. 8 is a top view of a portion of an exemplary electrode assembly;

FIG. 9 is a partial cross-sectional view of FIG. 8;

FIGS. 10A, 10B, 11, 12, and 13 are partial top views of exemplaryelectrode assemblies;

FIG. 14 is a partial cross-sectional view of an exemplary electrodeassembly;

FIGS. 15A, 15B, and 15C are temperature profiles taken throughcross-sections A-A, B-B-, and C-C, respectively, of the assembly of FIG.14; and

FIG. 16 is a graphical representation of the temperature profile atvarying distances from the center of an exemplary electrode.

While the disclosure is amenable to various modifications andalternative forms, specifics thereof have been shown by way of examplein the drawings and will be described in detail. It should beunderstood, however, that the intention is not to limit the invention tothe particular embodiments described. On the contrary, the intention isto cover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the disclosure.

DETAILED DESCRIPTION

The following description should be read with reference to the drawings,which are not necessarily to scale, wherein like reference numeralsindicate like elements throughout the several views. The detaileddescription and drawings are intended to illustrate but not limit theclaimed invention. Those skilled in the art will recognize that thevarious elements described and/or shown may be arranged in variouscombinations and configurations without departing from the scope of thedisclosure. The detailed description and drawings illustrate exampleembodiments of the claimed invention.

For the following defined terms, these definitions shall be applied,unless a different definition is given in the claims or elsewhere inthis specification.

All numeric values are herein assumed to be modified by the term“about,” whether or not explicitly indicated. The term “about”, in thecontext of numeric values, generally refers to a range of numbers thatone of skill in the art would consider equivalent to the recited value(i.e., having the same function or result). In many instances, the term“about” may include numbers that are rounded to the nearest significantfigure. Other uses of the term “about” (i.e., in a context other thannumeric values) may be assumed to have their ordinary and customarydefinition(s), as understood from and consistent with the context of thespecification, unless otherwise specified.

The recitation of numerical ranges by endpoints includes all numberswithin that range, including the endpoints (e.g. 1 to 5 includes 1, 1.5,2, 2.75, 3, 3.80, 4, and 5).

As used in this specification and the appended claims, the singularforms “a”, “an”, and “the” include plural referents unless the contentclearly dictates otherwise. As used in this specification and theappended claims, the term “or” is generally employed in its senseincluding “and/or” unless the content clearly dictates otherwise.

It is noted that references in the specification to “an embodiment”,“some embodiments”, “other embodiments”, etc., indicate that theembodiment(s) described may include a particular feature, structure, orcharacteristic, but every embodiment may not necessarily include theparticular feature, structure, or characteristic. Moreover, such phrasesare not necessarily referring to the same embodiment. Further, when aparticular feature, structure, or characteristic is described inconnection with an embodiment, it would be within the knowledge of oneskilled in the art to effect such feature, structure, or characteristicin connection with other embodiments, whether or not explicitlydescribed, unless clearly stated to the contrary. That is, the variousindividual elements described below, even if not explicitly shown in aparticular combination, are nevertheless contemplated as beingcombinable or arrangable with each other to form other additionalembodiments or to complement and/or enrich the described embodiment(s),as would be understood by one of ordinary skill in the art.

Certain treatments are aimed at tissue ablation. In some examples,tissue ablation may include the temporary or permanent interruption ormodification of select nerve function. In some embodiments, the nervesmay be sympathetic nerves. One example treatment is renal nerveablation, which is sometimes used to treat conditions such as or relatedto hypertension, congestive heart failure, diabetes, or other conditionsimpacted by high blood pressure or salt retention. The kidneys produce asympathetic response, which may increase the undesired retention ofwater and/or sodium. The result of the sympathetic response, forexample, may be an increase in blood pressure. Ablating some of thenerves running to the kidneys (e.g., disposed adjacent to or otherwisealong the renal arteries) may reduce or eliminate this sympatheticresponse, which may provide a corresponding reduction in the associatedundesired symptoms (e.g., a reduction in blood pressure).

Some embodiments of the present disclosure relate to a power generatingand control apparatus, often for the treatment of targeted tissue inorder to achieve a therapeutic effect. In some embodiments, the targettissue is tissue containing or proximate to nerves. In otherembodiments, the target tissue is sympathetic nerves, including, forexample, sympathetic nerves disposed adjacent to blood vessels. In stillother embodiments the target tissue is luminal tissue, which may furthercomprise diseased tissue such as that found in arterial disease.

In some embodiments of the present disclosure, the ability to deliverenergy in a targeted dosage may be used for nerve tissue in order toachieve beneficial biologic responses. For example, chronic pain,urologic dysfunction, hypertension, and a wide variety of otherpersistent conditions are known to be affected through the operation ofnervous tissue. For example, it is known that chronic hypertension thatmay not be responsive to medication may be improved or eliminated bydisabling excessive nerve activity proximate to the renal arteries. Itis also known that nervous tissue does not naturally possessregenerative characteristics. Therefore it may be possible tobeneficially affect excessive nerve activity by disrupting theconductive pathway of the nervous tissue. When disrupting nerveconductive pathways, it is particularly advantageous to avoid damage toneighboring nerves or organ tissue. The ability to direct and controlenergy dosage is well-suited to the treatment of nerve tissue. Whetherin a heating or ablating energy dosage, the precise control of energydelivery as described and disclosed herein may be directed to the nervetissue. Moreover, directed application of energy may suffice to target anerve without the need to be in exact contact, as would be required whenusing a typical ablation probe. For example, eccentric heating may beapplied at a temperature high enough to denature nerve tissue withoutcausing ablation and without requiring the piercing of luminal tissue.However, it may also be desirable to configure the energy deliverysurface of the present disclosure to pierce tissue and deliver ablatingenergy similar to an ablation probe with the exact energy dosage beingcontrolled by a power control and generation apparatus.

In some embodiments, efficacy of the denervation treatment can beassessed by measurement before, during, and/or after the treatment totailor one or more parameters of the treatment to the particular patientor to identify the need for additional treatments. For instance, adenervation system may include functionality for assessing whether atreatment has caused or is causing a reduction in neural activity in atarget or proximate tissue, which may provide feedback for adjustingparameters of the treatment or indicate the necessity for additionaltreatments.

Many of the devices and methods described herein are discussed relativeto renal nerve ablation and/or modulation. However, it is contemplatedthat the devices and methods may be used in other treatment locationsand/or applications where sympathetic nerve modulation and/or othertissue modulation including heating, activation, blocking, disrupting,or ablation are desired, such as, but not limited to: blood vessels,urinary vessels, or in other tissues via trocar and cannula access. Forexample, the devices and methods described herein can be applied tohyperplastic tissue ablation, cardiac ablation, pain management,pulmonary vein isolation, pulmonary vein ablation, tumor ablation,benign prostatic hyperplasia therapy, nerve excitation or blocking orablation, modulation of muscle activity, hyperthermia or other warmingof tissues, etc. The disclosed methods and apparatus can be applied toany relevant medical procedure, involving both human and non-humansubjects. The term modulation refers to ablation and other techniquesthat may alter the function of affected nerves and other tissue.

FIG. 1 is a schematic view of an example sympathetic nerve ablationsystem 100. System 100 may include a sympathetic nerve ablation device120. Sympathetic nerve ablation device 120 may be used to ablate nerves(e.g., renal nerves) disposed adjacent to the kidney K (e.g., renalnerves disposed about a renal artery RA). In use, sympathetic nerveablation device 120 may be advanced through a blood vessel such as theaorta A to a position within the renal artery RA. This may includeadvancing sympathetic nerve ablation device 120 through a guide sheathor catheter 14. When positioned as desired, sympathetic nerve ablationdevice 120 may be activated to activate one or more electrodes (notshown). This may include operatively coupling sympathetic nerve ablationdevice 120 to a control unit 110, which may include an RF generator, soas to supply the desired activation energy to the electrodes. Forexample, sympathetic nerve ablation device 120 may include a wire orconductive member 18 with a first connector 20 that can be connected toa second connector 22 on the control unit 110 and/or a wire 24 coupledto the control unit 110. In at least some embodiments, the control unit110 may also be utilized to supply/receive the appropriate electricalenergy and/or signal to activate one or more sensors disposed at or neara distal end of sympathetic nerve ablation device 120. When suitablyactivated, the one or more electrodes may be capable of ablating tissue(e.g., sympathetic nerves) as described below and the one or moresensors may be used to detect desired physical and/or biologicalparameters.

The sympathetic nerve ablation device 120 may include an elongatetubular member or catheter shaft 122. In some embodiments, the elongatetubular member or catheter shaft 122 may be configured to be slidinglyadvanced over a guidewire or other elongate medical device to a targetsite. In some embodiments, the elongate tubular member or catheter shaft122 may be configured to be slidingly advanced within a guide sheath orcatheter 14 to a target site. In some embodiments, the elongate tubularmember or catheter shaft 122 may be configured to be advanced to atarget site over a guidewire, within a guide sheath or catheter 14, or acombination thereof. An expandable member 130 may be disposed at, on,about, or near a distal region of the elongate tubular member orcatheter shaft 122. In some embodiments, the expandable member 130 maybe a compliant or a non-compliant balloon. In some embodiments, theexpandable member 130 may be capable of shifting between an unexpandedconfiguration and an expanded configuration.

The use of medical devices that include a balloon with one or moreelectrode assemblies coupled thereto, for example as described herein,may be desirable. In some instances, however, the electrode assembliesmay include relatively stiff and/or bulky materials or elements.Accordingly, when the balloon is deflated following a treatmentprocedure, the electrode assembly may tend to flatten and/or widen out.When so configured, the one or more electrode assemblies, and/orcomponents or edges thereof, might catch on the edge of a guide catheterwhen proximally retracting the medical device (e.g., including theaffixed electrode assemblies) into the guide catheter. Disclosed hereinare medical devices that include structural features that may reduce thesize of an electrode assembly and the likelihood of an electrodeassembly or other structures of the medical device “catching” on the endof a guide catheter (or other device) when being retracted, for example,into the guide catheter, thus resulting in reduced withdrawal forces.

The electrode assemblies may be arranged on the expandable member andeach assembly may include one or more of each of a ground electrode 10,a positive electrode 12, and a temperature sensor or thermistor 26. Someprior art electrode pair designs consisted of an electrode pad 70 havinga plurality of ground electrodes 10 spaced a few millimeters apart froma plurality of positive electrodes 12, with a thermistor 26 placed inbetween the electrodes, as shown in FIG. 2A. This allows for accuratetemperature sensing when individual electrodes are activated, creatingconsistent lesions. Each individual electrode pair may be activatedindividually, resulting in staggered treatment around the vessel. Whenthe electrode assemblies are placed on a balloon catheter, they may bewired to individually activate around each thermistor, as shown in FIG.2B.

In other applications, more complete and circumferential treatment maybe desired. In such applications, the electrode pairs may be arranged tofire within pairs, indicated by arrows 50, and in between pairs,indicated by arrows 60. See FIG. 3. In this scenario, the in betweenpairs of electrodes do not have thermistors to monitor temperatureduring activation.

In order to monitor the temperature of the in-between electrode pairs,additional thermistors 26 may be placed between the electrode pads 70,as shown in FIG. 4. However, this arrangement requires doubling thenumber of thermistors, which requires additional surface area on theballoon, may increase the stiffness and profile of the balloon, andrequires additional electrical connections to complete the circuit forthe additional thermistors. The thermistor may be the largest componentof the electrode assembly. For example, a thermistor may be 0.02 inches(0.0508 centimeter) by 0.04 inches (0.1016 centimeter) and 0.006 inches(0.01524 centimeter) thick. When placed between the electrodes, thethermistor may increase the circuit profile and circuit area/mass. Thisstructure may also make the expandable member difficult to fold,requiring a larger catheter or sheath.

In some embodiments, an off-center placement of the temperature sensoron a bipolar electrode structure may reduce the flexible circuit profileand improve balloon foldability, allowing the balloon to pass through asmaller sheath or catheter. Moving the temperature sensor off center, orin line with the electrodes may allow the expandable member to foldalong the center of the two rows of electrodes without breaking thetemperature sensors. During retraction of the balloon, the temperaturesensor may be pulled back with the spine of the flexible circuit wherethe electrodes are disposed. The middle part between the two rows ofelectrodes is easier to fold. This structure may allow the device to beinserted and withdrawn through a smaller sheath or catheter.

An example temperature sensor placement is shown in FIG. 5, whichprovides full temperature monitoring for both within pair and in-betweenpair electrode activation without increasing the number of temperaturesensors. The temperature sensor 226, such as a thermistor, is placedunder the ground electrode 210, as shown in FIG. 5. A layer ofinsulation material, such as polyimide, may be placed between the groundelectrode 210 and the temperature sensor 226. In this arrangement, eachtemperature sensor 226 may monitor the temperature of within pairelectrode activation 50 and in-between pair electrode activation 60, asshown in FIG. 6A. The firing frequency and sequence may be controlled bythe generator hardware and software, which may optimize temperatureaccuracy and may reduce the amount of cross-talk during electrodeactivation and temperature sensing. In some embodiments, longer balloonsmay be desired. The electrode assemblies 140 may be lengthened andadditional electrodes 222, including both ground electrodes 210 andactive positive electrodes 212, and temperature sensors 226 may be addedin arrays extending along the length of the electrode to monitor thetemperature across the entire length. See FIG. 6B. The electrode arraysmay be oriented parallel to each other or at an angle to each other, andmay be spaced apart. In some embodiments, the area 145 of the electrodeassembly between the arrays of electrodes 210, 212 is devoid ofcircuitry. This area 145 devoid of circuitry may aid in folding theelectrode assemblies.

Each electrode assembly 140 may include a plurality of discreteconductive traces layered on top of a base layer 202. The plurality ofdiscrete conductive traces may include a ground electrode trace 210, anactive or positive electrode trace 212, and a temperature sensor trace214. The ground electrode trace 210 may include an elongated groundelectrode support 216, and the active electrode trace 212 may include anelongated active electrode support 217. The electrode supports 216, 217may taper down in width at their proximal ends to provide a desiredamount of flexibility, however, this is not required. Generally, thecurvature of the traces where necking is shown may be optimized toreduce balloon recapture forces and to reduce the potential for anysnagging that sharper contours may present. The shape and position ofthe traces may also be optimized to provide dimensional stability to theelectrode assembly 140 as a whole, so as to prevent distortion duringdeployment and use.

As shown in FIG. 6B, the ground electrode trace 210 and active electrodetrace 212 may each include a plurality of electrodes 222. In someembodiments, at least one electrode may be provided for each electrodetrace, however, more or less may be used. For example, in someembodiments, three electrodes may be provided for each electrode trace.See FIGS. 11-13. In other embodiments, up to 35 or more electrodes maybe provided for each electrode trace, as shown in FIGS. 7 and 8. Theplurality of electrodes 222 may protrude above and/or extend through theinsulating layer 206. In some embodiments, the plurality of electrodes222 may include at least one active electrode and at least one groundelectrode attached and/or electrically connected to the elongated activeelectrode support 217 and the elongated ground electrode support 216,respectively. In some embodiments, a plurality of electrodes 222 may beattached and/or electrically connected to the elongated ground electrodesupport 216, thereby defining a plurality of ground electrodes, and/orthe elongated active electrode support 217, thereby defining a pluralityof active electrodes.

In some embodiments, the plurality of electrodes 222 may be from about0.030 mm thick to about 0.070 mm thick. In some embodiments, theplurality of electrodes 222 may be about 0.051 mm thick. In someembodiments, the plurality of electrodes 222 may extend about 0.020 mmto about 0.050 mm above the insulating layer 206. In some embodiments,the plurality of electrodes 222 may extend about 0.038 mm above theinsulating layer 206. Additionally, each electrode may have radiusedcorners to reduce tendency to snag on other devices and/or tissue.Although the above description of the plurality of electrodes and thetraces associated with them has been described in the context of abi-polar electrode assembly, those of skill in the art will recognizethat the same electrode assembly may function in a monopolar mode aswell. For instance, as one non-limiting example, the plurality ofelectrodes associated with active electrode trace 212 may be used asmonopolar electrodes, with ground electrode trace 210 disconnectedduring energization of those electrodes.

In some embodiments, the temperature sensor 226 may have a length ofabout 0.100 mm to about 2.000 mm, and a width of about 0.100 mm to about0.800 mm. In some embodiments, the temperature sensor 226 may have alength of about 1.000 mm and a width of about 0.500 mm. In anotherembodiment, the temperature sensor may have a length of about 0.2 mm anda width of 0.01 mm. Other sizes and/or dimensions are contemplated.

In some embodiments the electrodes may be canted around the balloon at aslight angle to form a helical configuration around the balloon, whichmay aid in retraction of the balloon after treatment. For example, asshown in FIG. 7, a plurality of electrode assemblies 140 may bepositioned at an angle on the expandable member 130, shown in anexpanded state. The electrode assemblies 140 may be configured such thatenergy applied by the electrode assemblies create treatments that may ormay not overlap. Treatments applied by the electrode assemblies 140 maybe circumferentially continuous or non-continuous along longitudinalaxis L-L. The energy applied by the electrode assemblies, such as theelectrode assemblies 140 shown in FIG. 7, may overlap, longitudinally,circumferentially, and/or in other ways, to at least some extent. Theelectrode assembly 140 shown in FIGS. 7 and 8 may include a base layer202 in a rectangular shape. This is not intended to be limiting. Othershapes are contemplated. Additionally, the electrode assembly 140 mayinclude a plurality of openings extending therethrough to provide foradded flexibility, and the portions of the assemblies may includerounded or curved corners, transitions and other portions. In someinstances, the openings and rounded/curved features may enhance theassembly's resistance to delamination from the expandable member 130, asmay occur, in some instances, when the expandable member 130 isrepeatedly expanded and collapsed (which may also entail deployment fromand withdrawal into a protective sheath), such as may be needed whenmultiple sites are treated during a procedure.

One example electrode assembly 140 is illustrated in FIG. 8. As shown inFIG. 8, each electrode assembly 140 may include one or more temperaturesensor 226 on a sensor trace 214, a plurality of electrodes 222, somedisposed on a ground array or trace 210 and some disposed on an activeor positive array or trace 212. The sensor trace 214 may be centrallylocated on the electrode assembly 140. In other examples, the sensortrace 214 may be located adjacent one of the arrays or traces 210, 212.Each electrode assembly 140 includes a proximal tail 180 which mayinclude a narrowed region extending off the proximal end of theexpandable member 130 and along the catheter shaft 122 to a proximal endof the catheter shaft 122.

In some embodiments, the temperature sensor 226 may be a thermistor. Asshown in FIG. 9, the temperature sensor 226 may be disposed on anon-tissue contacting side (i.e., bottom side) of the electrode assembly140. Accordingly, the temperature sensor 226 may be captured between theelectrode assembly 140 and the expandable member 130 when incorporatedinto an ablation device 120. This may be advantageous sincesurface-mounted electrical components, like thermistors, may typicallyhave sharp edges and corners, which may get caught on tissue andpossibly cause problems in balloon deployment and/or retraction. Thisarrangement may also keep soldered connections from making contact withblood, since solder is typically non-biocompatible.

The size and/or thickness of the electrode assembly 140 at thetemperature sensor 226 may create a protrusion extending outward fromthe outer surface of the expandable member 130. Following a treatmentprocedure, the expandable member 130 may be collapsed to a collapseddelivery configuration, as discussed further herein, and the ablationdevice 120 may be retracted within the guide sheath or catheter 14.Significant protrusion(s) may make retraction into the guide sheath orcatheter 14 more difficult and/or require a larger diameter guide sheathor catheter 14 than would otherwise be desired. Additionally, theprotrusion(s) may negatively impact the foldability characteristics ofthe expandable member 130, both for delivery and for withdrawal.

FIG. 9 shows a partial top view of an example electrode assembly 140 anda cross section thereof. In the cross-sectional view of FIG. 9, thebottom of the figure is the portion of the electrode assembly 140 thatmay face, may be in contact with, and/or may be attached and/or bondeddirectly to an outer surface of the expandable member 130. In someembodiments, a base layer 202 of insulation which may provide afoundation for the electrode assembly 140. The base layer 202 may beconstructed from a polymer such as polyimide, although other materialsare contemplated. In some embodiments, the base layer 202 may be about0.010 mm to about 0.020 mm thick. In some embodiments, the base layer202 may be about 0.015 mm thick. Other suitable thicknesses are alsocontemplated. For reference, the base layer 202 may form the majority ofthe bottom side of the electrode assembly 140 that may face, may be incontact with, and/or may be attached and/or bonded directly to the outersurface of the expandable member 130.

A first conductive layer 204 may include a plurality of discreteconductive traces layered on the base layer 202. In some embodiments,the plurality of discrete conductive traces may be separated laterallyby a non-conductive material. The plurality of discrete conductivetraces of the conductive layer 204 may include, for example, a layer ofelectrodeposited copper or rolled-annealed copper. Other suitableconductive materials are also contemplated. In some embodiments, theconductive layer 204 and/or the plurality of discrete conductive tracesmay be about 0.010 mm to about 0.030 mm thick. In some embodiments, theconductive layer 204 and/or the plurality of discrete conductive tracesmay be about 0.018 mm thick. Other suitable thicknesses are alsocontemplated. The first conductive layer 204 may be etched to form thepositive and ground connection for the temperature sensor 226, which maybe placed over the first conductive layer.

A second conductive layer 304 may be disposed over the base layer 202,and an insulating layer 206 may be discretely or continuously layered ontop of the second conductive layer 304, such that the second conductivelayer 304 may be fluidly sealed between the base layer 202 and theinsulating layer 206. In other words, the insulating layer 206 may forma top side or surface of the electrode assembly 140 that may face awayfrom the outer surface of the expandable member 130. The relationshipbetween the base layer 202, the first conductive layer 204, the secondconductive layer 304, and the insulating layer 206 is illustrative, andother constructions are contemplated. Like the base layer 202, theinsulating layer 206 may be constructed from a polymer such aspolyimide, although other materials are contemplated. In someembodiments, the insulating layer 206 may be from about 0.010 mm thickto about 0.020 mm thick. In some embodiments, the insulating layer 206may be about 0.013 mm thick. Other suitable thicknesses are alsocontemplated. In some embodiments, the insulating layer 206 may be acomplete or partial polymer coating, such as PTFE or silicone. Othermaterials are also contemplated.

The electrode assembly 140 may be constructed as a flexible circuithaving a plurality of layers. Such layers may be continuous ornon-contiguous (i.e., made up of discrete portions). The electrodeassembly 140 may be a multiple layer structure with an electrode 222 onan upper surface (away from the expandable member) and a temperaturesensor such as a temperature sensor 226 on a lower surface (against theexpandable member). The electrode assembly 140 may include one or morelayers of polymer and one or more layers of a conductive material. Asshown in cross-section in FIG. 9, the electrode assembly 140 may includetwo polymer layers 202, 206, two conductive layers 204, 304, atemperature sensor 226, and an electrode 222. The polymer and conductivelayers may be laminated sheets of a polymer layer 202, 206 adhesivelybonded to a conductive layer 204, 304. In some embodiments, two suchsheets may be bonded together with an adhesive layer 205. As shown inFIG. 9, two polymer/conductive sheets may be bonded together with apolymer side against a conductive side, resulting in an alternatingpolymer 206-conductive 304-adhesive 205-polymer 202-conductive 204structure, when a cross-section is taken starting with the upper surface(away from the expandable member).

The second conductive layer 304 may be etched to form traces for theground and positive electrode 222 pairs. A via 204v may be created toconnect the electrode ground trace of the second conductive layer 304 tothe temperature sensor 226 and ground trace of the first conductivelayer 204. The temperature sensor 226 may be soldered onto the firstconductive layer 204. The insulation layer 206 may be skived to form arecess 208 to allow for gold plating to form gold electrodes 222.

In other embodiments, shown in FIG. 10A, one of the ground electroderecesses may be removed and the temperature sensor 226 may be positionedin the region where the recess would have been. The recess 208 may beoriented in any direction. The first conductive layer 204 may bedesigned to share the ground trace 210 with the temperature sensor 226while a new trace may be formed for the positive connection of thetemperature sensor. For longer electrodes that may require moretemperature sensors, the temperature sensors may be positioned along theground trace 210 and may be wired in parallel with each other as shownin FIG. 10B. Alternatively, when multiple temperature sensors are used,they may be wired separately (not shown).

In some embodiments, the electrode assembly(s) 140 may be disposed alongor otherwise define pre-determined fold lines along which the expandablemember 130 may fold after deflation. In some embodiments, thepre-determined fold lines may aid in re-folding of the expandable member130. In some embodiments, the electrode assembly(s) 140 may besubstantially linear, extending along or at an angle to the longitudinalaxis L-L along the entire length of the expandable member 130. In someembodiments, the electrode assemblies may extend parallel to thelongitudinal axis in a proximal region, and then be bent into an angledorientation in a distal region (not shown). The electrode assembly(s)140 may cause the balloon to fold along the lines of the electrodeassembly(s) 140, reducing the withdrawal force needed to withdraw theablation device 120 into the guide sheath or catheter 14, and allowingthe use of a smaller diameter guide sheath. For example, a 6 Fr or 7 Frguide catheter 14 may be used, providing advantages in certainprocedures, (e.g., renal procedures), where 8 Fr guide catheters havebeen previously used. The electrode assembly(s) 140 may also reduceshear force or improve balloon refold profile efficiency, therebyreducing delamination of the electrode assembly(s) 140 from theexpandable member 130.

In some embodiments, the electrode assemblies 140 include a single rowor array of positive electrodes 212 and a single row or array of groundelectrodes 210, as shown in FIG. 8. In other embodiments, the electrodeassemblies 340, 440 may include longitudinally spaced apart electrodepads 308, 336 and 408, 436, as shown in FIGS. 11A and 11B. Movingproximally from the distal electrode pad 308, 408, the combined baselayer 202, conductive layer 304, and insulating layer 206 may reduce inlateral width to an intermediate tail 328, 428. Continuing to moveproximally from the intermediate tail 328, 428, the combined base layer202, conductive layer 304, and insulating layer 206 may increase inlateral width to form a proximal electrode pad 336, 436. The proximalelectrode pad 336, 436 may be constructed similarly to the distalelectrode pad 308, 408. However, as shown, the proximal electrode pad336, 436 may be laterally offset from the distal electrode pad 308, 408with respect to a central longitudinal axis extending along theelectrode assembly 340, 440.

From the proximal electrode pad 336, 436, the combined base layer 202,conductive layer 304, and insulating layer 206 may reduce in lateralwidth to form a proximal tail 338, 438. The proximal tail 338, 438 mayinclude connectors (not shown) to enable coupling to one or moresub-wiring harnesses and/or connectors and ultimately to control unit110. Each of these lines may be extended along parallel respective axeswith respect to the central axis of the electrode assembly 340, 440.

The electrode assembly 340, 440 may have a symmetric or an asymmetricarrangement of the distal electrode pad 308, 408 and proximal electrodepad 336, 436, about the central axis of the electrode assembly 340, 440.Further, the ground electrodes 210 of both electrode pads may besubstantially aligned along the central axis, along with the groundlines. It has been found that this arrangement may present certainadvantages. For example, by essentially sharing the same ground trace,the width of the proximal tail may be only about one and a half timesthat of the intermediate tail, rather than being approximately twice aswide if each electrode pad had independent ground lines. Thus, theproximal tail 338, 438 may be narrower than two intermediate tails 328,428 positioned side-by-side.

FIG. 11A illustrates an electrode assembly 340 with linear rows ofpositive electrodes 212 and ground electrodes 210, where substratematerial, including a base layer 202, extends between the rows. FIG. 11Billustrates a similar electrode assembly 440 with the substrate materialcut out between the linear rows of electrodes 212, 210. The removal ofsubstrate material between the rows of electrodes reduces the mass ofthe circuit that must be folded. When disposed on a balloon, theelectrode assembly 440 may provide enhanced foldability as compared toelectrode assembly 340 because lack of substrate between the linear rowsof electrodes may allow for easier folding between the electrode rows,with the temperature sensor 226 being folded with the ground electrodes210. This structure may allow the device to be inserted and withdrawnthrough a smaller sheath or catheter. However, even with the base layer202 present between the rows of electrodes, as shown in FIG. 11A, movingthe temperature sensor 226 away from the center and onto a row ofelectrodes provides enhanced foldability over the prior art electrodeassemblies shown in FIGS. 2A and 2B. The electrode assemblies 340, 440shown in FIGS. 11A and 11B also show a temperature sensor 226 placed inline with and proximal of the most proximal ground electrode 210. Thisconfiguration provides the electrodes and temperature sensors in twolinear rows, which may aid in folding the electrode assembly along aline between the rows of electrodes.

In some embodiments, the temperature sensor 226 may be a sputteredthermocouple (for example, Type T configuration: Copper/Constantan). Inthe embodiment illustrated in FIGS. 12A and 12B, the temperature sensoris a thermocouple 426 with a junction close to the middle electrode onthe ground trace 210. The middle electrode may have less variation dueto apposition of the balloon and may have better correlation or error tothe prior art center position. In some embodiments, the thermocouple mayinclude separate layers of copper and constantan. The thermocouple canbe formed by a through hole between the two layers and may be filledwith solder, which makes the through hole the thermocouple junction. Asin FIGS. 11A and 11B, FIG. 12A shows an electrode assembly 440 withsubstrate or base layer 402 disposed between the ground trace 210 andthe positive trace 212, while FIG. 12B shows an electrode assembly 540with the substrate removed between the rows of positive and negativeelectrodes.

The thermocouple junction may be placed on or near a proximal groundelectrode, as shown in FIGS. 13A and 13B. The thermal junction may bemade of copper and constantan (T-type), instead of gold and constantan.However, the junction is close to the copper layer so it can measure theexact temperature of the heating element. A thermocouple may generate avoltage differential at the junction of two dissimilar metals based uponthe temperature at the junction, as is known in the art. In someembodiments, an isothermal junction may be formed at a proximal end ofthe electrode assembly 140, spaced apart from and thermally isolatedfrom the electrode pad(s) and/or the plurality of electrodes. In someembodiments, the temperature sensor 226 may be formed as a discretetrace of electrodeposited copper within the conductive layer 204. Insome embodiments, the distal end portion of the sensor trace 214, and insome cases the entire sensor trace 214 may be formed from, for example,constantan (i.e., copper-nickel alloy), nickel-chromium, or othersuitable conductive material.

FIG. 13A shows another embodiment of electrode assembly 640 havingparallel rows of ground electrodes 210 and positive electrodes 212 on asubstrate or base layer 502. The temperature sensor 526 may be athermocouple with a junction at the proximal end of the proximal-mostground electrode 210. FIG. 13B shows a similar electrode assembly 740with a portion of the base layer 502 removed between the rows of groundelectrodes 210 and positive electrodes 212.

Exemplary devices have a very uniform temperature profile on the balloonand inside tissue during RF delivery due to their balloon structure andbipolar energy delivery. FIG. 14 is a cross-sectional view of asimplified model electrode assembly 840 with electrodes 822, conductivelayer 804, and base layer or substrate 802. FIGS. 15A-15C show thermalprofiles of various surfaces at 30 seconds of heating. FIG. 15A showsthe surface of polyimide base layer 802, through section A-A in FIG. 14.FIG. 15B shows the interface between a copper conductive layer 804 andthe polyimide base layer 802, through section B-B in FIG. 14. FIG. 15Cshows the balloon outer diameter at section C-C in FIG. 14. As can beseen when comparing FIGS. 15A-15C, the temperature profile isessentially constant across the cross-section of the electrode assembly840. The temperature at the center of the balloon 1501 is close to thetemperature at the electrodes 1502. Because of this consistency, thetemperature at the center of the balloon 1501 is also close to and wellcorrelated with the temperature at the edge of the electrode assembly1502.

FIG. 16 illustrates the temperature at the center of an electrode pair1601 and at various distances from the center. As can be seen, thetemperature is essentially constant from the center of the electrodepair to the edge of the row of electrodes. A temperature measurementnear an electrode has been found to be suitable for temperature controlinstead of a center temperature measurement, while maintaining lesionconsistency.

In use, the ablation device 120 may be advanced through a blood vesselor body passageway to a position adjacent to a target tissue (e.g.,within a renal artery), in some cases with the aid of a delivery sheathor catheter 14. In some embodiments, the target tissue may be one ormore sympathetic nerves disposed about the blood vessel. In someembodiments, the control unit 110 may be operationally coupled to theablation device 120, which may be inserted into a blood vessel or bodypassageway such that an expandable member 130 (having a plurality ofelectrode assemblies 300) may be placed adjacent to the target tissuewhere therapy is required. Placement of the ablation device 120 adjacentthe target tissue where therapy is required may be performed accordingto conventional methods, (e.g., over a guidewire under fluoroscopicguidance). When suitably positioned, the expandable member 130 may beexpanded from a collapsed delivery configuration to an expandedconfiguration, for example by pressurizing fluid from about 2-10 atm inthe case of a balloon. This may place/urge the plurality of electrodesagainst the wall of the blood vessel. The plurality of active electrodesmay be activated. Ablation energy may be transmitted from the pluralityof active electrodes through the target tissue (where sympathetic nervesmay be ablated, modulated, or otherwise impacted), and back through theplurality of ground electrodes, in a bipolar configuration, or backthrough the common ground electrode, in a monopolar configuration.Following treatment, the expandable member 130 may be collapsed to thecollapsed delivery configuration for retraction into the guide sheath orcatheter 14 and subsequent withdrawal from the blood vessel or bodypassageway.

The materials that can be used for the various components of theablation device 120 (and/or other devices disclosed herein) may includethose commonly associated with medical devices. For simplicity purposes,the following discussion makes reference to the ablation device 120.However, this is not intended to limit the devices and methods describedherein, as the discussion may be applied to other similar tubularmembers and/or expandable members and/or components of tubular membersand/or expandable members disclosed herein.

The ablation device 120 and the various components thereof may be madefrom a metal, metal alloy, polymer (some examples of which are disclosedbelow), a metal-polymer composite, ceramics, combinations thereof, andthe like, or other suitable material. Some examples of suitable polymersmay include polytetrafluoroethylene (PTFE), ethylene tetrafluoroethylene(ETFE), fluorinated ethylene propylene (FEP), polyoxymethylene (POM, forexample, DELRIN® available from DuPont), polyether block ester,polyurethane (for example, Polyurethane 85A), polypropylene (PP),polyvinylchloride (PVC), polyether-ester (for example, ARNITEL®available from DSM Engineering Plastics), ether or ester basedcopolymers (for example, butylene/poly(alkylene ether) phthalate and/orother polyester elastomers such as HYTREL® available from DuPont),polyamide (for example, DURETHAN® available from Bayer or CRISTAMID®available from Elf Atochem), elastomeric polyamides, blockpolyamide/ethers, polyether block amide (PEBA, for example availableunder the trade name PEBAX®), ethylene vinyl acetate copolymers (EVA),silicones, polyethylene (PE), Marlex high-density polyethylene, Marlexlow-density polyethylene, linear low density polyethylene (for exampleREXELL®), polyester, polybutylene terephthalate (PBT), polyethyleneterephthalate (PET), polytrimethylene terephthalate, polyethylenenaphthalate (PEN), polyetheretherketone (PEEK), polyimide (PI),polyetherimide (PEI), polyphenylene sulfide (PPS), polyphenylene oxide(PPO), poly paraphenylene terephthalamide (for example, KEVLAR®),polysulfone, nylon, nylon-12 (such as GRILAMID® available from EMSAmerican Grilon), perfluoro(propyl vinyl ether) (PFA), ethylene vinylalcohol, polyolefin, polystyrene, epoxy, polyvinylidene chloride (PVdC),poly(styrene-b-isobutylene-b-styrene) (for example, SIBS and/or SIBS50A), polycarbonates, ionomers, biocompatible polymers, other suitablematerials, or mixtures, combinations, copolymers thereof, polymer/metalcomposites, and the like. In some embodiments the sheath can be blendedwith a liquid crystal polymer (LCP). For example, the mixture cancontain up to about 6 percent LCP.

Some examples of suitable metals and metal alloys include stainlesssteel, such as 304V, 304 L, and 316LV stainless steel; mild steel;nickel-titanium alloy such as linear-elastic and/or super-elasticnitinol; other nickel alloys such as nickel-chromium-molybdenum alloys(e.g., UNS: N06625 such as INCONEL® 625, UNS: N06022 such as HASTELLOY®C-22®, UNS: N10276 such as HASTELLOY® C276®, other HASTELLOY® alloys,and the like), nickel-copper alloys (e.g., UNS: N04400 such as MONEL®400, NICKELVAC® 400, NICORROS® 400, and the like),nickel-cobalt-chromium-molybdenum alloys (e.g., UNS: R30035 such asMP35-N® and the like), nickel-molybdenum alloys (e.g., UNS: N10665 suchas HASTELLOY® ALLOY B2®), other nickel-chromium alloys, othernickel-molybdenum alloys, other nickel-cobalt alloys, other nickel-ironalloys, other nickel-copper alloys, other nickel-tungsten or tungstenalloys, and the like; cobalt-chromium alloys; cobalt-chromium-molybdenumalloys (e.g., UNS: R30003 such as ELGILOY®, PHYNOX®, and the like);platinum enriched stainless steel; titanium; combinations thereof; andthe like; or any other suitable material.

As alluded to herein, within the family of commercially availablenickel-titanium or nitinol alloys, is a category designated “linearelastic” or “non-super-elastic” which, although may be similar inchemistry to conventional shape memory and super elastic varieties, mayexhibit distinct and useful mechanical properties. Linear elastic and/ornon-super-elastic nitinol may be distinguished from super elasticnitinol in that the linear elastic and/or non-super-elastic nitinol doesnot display a substantial “superelastic plateau” or “flag region” in itsstress/strain curve like super elastic nitinol does. Instead, in thelinear elastic and/or non-super-elastic nitinol, as recoverable strainincreases, the stress continues to increase in a substantially linear,or a somewhat, but not necessarily entirely linear relationship untilplastic deformation begins or at least in a relationship that is morelinear that the super elastic plateau and/or flag region that may beseen with super elastic nitinol. Thus, for the purposes of thisdisclosure linear elastic and/or non-super-elastic nitinol may also betermed “substantially” linear elastic and/or non-super-elastic nitinol.

In some cases, linear elastic and/or non-super-elastic nitinol may alsobe distinguishable from super elastic nitinol in that linear elasticand/or non-super-elastic nitinol may accept up to about 2-5% strainwhile remaining substantially elastic (e.g., before plasticallydeforming) whereas super elastic nitinol may accept up to about 8%strain before plastically deforming. Both of these materials can bedistinguished from other linear elastic materials such as stainlesssteel (that can also can be distinguished based on its composition),which may accept only about 0.2 to 0.44 percent strain beforeplastically deforming.

In some embodiments, the linear elastic and/or non-super-elasticnickel-titanium alloy is an alloy that does not show anymartensite/austenite phase changes that are detectable by differentialscanning calorimetry (DSC) and dynamic metal thermal analysis (DMTA)analysis over a large temperature range. For example, in someembodiments, there may be no martensite/austenite phase changesdetectable by DSC and DMTA analysis in the range of about −60 degreesCelsius (° C.) to about 120° C. in the linear elastic and/ornon-super-elastic nickel-titanium alloy. The mechanical bendingproperties of such material may therefore be generally inert to theeffect of temperature over this very broad range of temperature. In someembodiments, the mechanical bending properties of the linear elasticand/or non-super-elastic nickel-titanium alloy at ambient or roomtemperature are substantially the same as the mechanical properties atbody temperature, for example, in that they do not display asuper-elastic plateau and/or flag region. In other words, across a broadtemperature range, the linear elastic and/or non-super-elasticnickel-titanium alloy maintains its linear elastic and/ornon-super-elastic characteristics and/or properties.

In some embodiments, the linear elastic and/or non-super-elasticnickel-titanium alloy may be in the range of about 50 to about 60 weightpercent nickel, with the remainder being essentially titanium. In someembodiments, the composition is in the range of about 54 to about 57weight percent nickel. One example of a suitable nickel-titanium alloyis FHP-NT alloy commercially available from Furukawa Techno Material Co.of Kanagawa, Japan. Some examples of nickel titanium alloys aredisclosed in U.S. Pat. Nos. 5,238,004 and 6,508,803, which areincorporated herein by reference. Other suitable materials may includeULTANIUM™ (available from Neo-Metrics) and GUM METAL™ (available fromToyota). In some other embodiments, a superelastic alloy, for example asuperelastic nitinol can be used to achieve desired properties. In atleast some embodiments, portions of the ablation device 120 may also bedoped with, made of, or otherwise include a radiopaque material.Radiopaque materials are understood to be materials capable of producinga relatively bright image on a fluoroscopy screen or another imagingtechnique during a medical procedure. This relatively bright image aidsthe user of the ablation device 120 in determining its location. Someexamples of radiopaque materials can include, but are not limited to,gold, platinum, palladium, tantalum, tungsten alloy, polymer materialloaded with a radiopaque filler, and the like. Additionally, otherradiopaque marker bands and/or coils may also be incorporated into thedesign of the ablation device 120 to achieve the same result.

In some embodiments, a degree of Magnetic Resonance Imaging (MRI)compatibility may be imparted into the ablation device 120. For example,portions of device, may be made of a material that does notsubstantially distort the image and create substantial artifacts (i.e.,gaps in the image). Certain ferromagnetic materials, for example, maynot be suitable because they may create artifacts in an MRI image. Insome of these and in other embodiments, portions of the ablation device120 may also be made from a material that the MRI machine can image.Some materials that exhibit these characteristics include, for example,tungsten, cobalt-chromium-molybdenum alloys (e.g., UNS: R30003 such asELGILOY®, PHYNOX®, and the like), nickel-cobalt-chromium-molybdenumalloys (e.g., UNS: R30035 such as MP35-N® and the like), nitinol, andthe like, and others.

U.S. Patent application Ser. No. 13/750,879, filed on Jan. 25, 2013, nowU.S. Patent Publication No. US20130165926A1 is herein incorporated byreference.

It should be understood that this disclosure is, in many respects, onlyillustrative. Changes may be made in details, particularly in matters ofshape, size, and arrangement of steps without exceeding the scope of thedisclosure. This may include, to the extent that it is appropriate, theuse of any of the features of one example embodiment being used in otherembodiments. The invention's scope is, of course, defined in thelanguage in which the appended claims are expressed.

What is claimed is:
 1. A medical device for tissue ablation, comprising:a catheter shaft; an expandable member coupled to the catheter shaft,the expandable member being capable of shifting between an unexpandedconfiguration and an expanded configuration; and a plurality of elongateelectrode assemblies each constructed as a flexible circuit, theplurality of elongate electrode assemblies disposed on an outer surfaceof the expandable member; wherein each of the plurality of elongateelectrode assemblies includes one or more temperature sensors and aplurality of pairs of electrodes; and wherein the one or moretemperature sensors is positioned between the plurality of pairs ofelectrodes.
 2. The medical device of claim 1, wherein the one or moretemperature sensors positioned between the plurality of pairs ofelectrodes is positioned on a plurality of electrode pads.
 3. Themedical device of claim 1, wherein the one or more temperature sensorspositioned between the plurality of pairs of electrodes is positioned onthe outer surface of the expandable member.
 4. The medical device ofclaim 1, wherein each of the plurality of elongate electrode assembliesis formed from a multiple-layer structure comprising a first laminatedsheet including a first polymer layer laminated to a first conductivelayer and a second laminated sheet including a second polymer layerlaminated to a second conductive layer.
 5. The medical device of claim4, wherein the first and second laminated sheets are arranged with thefirst conductive layer of the first laminated sheet attached to thesecond polymer layer of the second laminated sheet.
 6. The medicaldevice of claim 4, wherein the one or more temperature sensors areattached to the second conductive layer of the second laminated sheetand are positioned at a lower surface of the multiple-layer structurefacing radially toward the expandable member.
 7. The medical device ofclaim 4, wherein the plurality of pairs of electrodes are formed in thefirst polymer layer of the first laminated sheet and are positioned atan upper surface of the multiple-layer structure facing radially awayfrom the expandable member.
 8. The medical device of claim 4, wherein avia connects the first and second conductive layers.
 9. The medicaldevice of claim 4, wherein the first and second conductive layers arecopper layers.
 10. The medical device of claim 1, wherein each pair ofthe plurality of pairs of electrodes includes an active electrode andground electrode, and wherein each of the plurality of elongateelectrode assemblies includes a plurality of the active electrodes, aplurality of the ground electrodes, and a plurality of the one or moretemperature sensors.
 11. The medical device of claim 1, wherein eachpair of the plurality of pairs of electrodes includes an activeelectrode and a ground electrode, and wherein each of the plurality ofelongate electrode assemblies includes a plurality of active electrodesaligned linearly, a plurality of the ground electrodes aligned linearlyand spaced apart from the plurality of the active electrodes, and aplurality of the one or more of the temperature sensors positioned atleast partially under the plurality of the ground electrodes.
 12. Amedical device for tissue ablation, comprising: an expandable memberconfigured to be coupled to a catheter shaft; and a plurality ofelongate electrode assemblies each constructed as a flexible circuit,the plurality of elongate electrode assemblies disposed on an outersurface of the expandable member; wherein each of the plurality ofelongate electrode assemblies includes one or more temperature sensorsand a plurality of pairs of electrodes; wherein the one or moretemperature sensors is positioned between the plurality of pairs ofelectrodes; wherein each pair of the plurality of pairs of electrodescomprises an active electrode and a ground electrode; and wherein atleast one of the one or more temperature sensors is positioned betweenthe active electrode and the ground electrode of at least one pair ofthe plurality of pairs of electrodes.
 13. The medical device of claim12, wherein the plurality of the one or more temperature sensorspositioned between the plurality of pairs of electrodes is positioned ona plurality of electrode pads.
 14. The medical device of claim 12,wherein the plurality of the one or more temperature sensors positionedbetween the plurality of pairs of electrodes is positioned on the outersurface of the expandable member.
 15. The medical device of claim 12,wherein each of the plurality of elongate electrode assemblies is formedfrom a multiple-layer structure comprising a first laminated sheetincluding a first polymer layer laminated to a first conductive layerand a second laminated sheet including a second polymer layer laminatedto a second conductive layer.
 16. The medical device of claim 12,wherein each of the plurality of elongate electrode assemblies includesa plurality of the active electrodes, a plurality of the groundelectrodes, and a plurality of the one or more temperature sensors,wherein each of the plurality of the one or more temperature sensors ispositioned at least partially under one of the ground electrodes. 17.The medical device of claim 12, wherein each of the plurality ofelongate electrode assemblies includes a plurality of the activeelectrodes aligned linearly, a plurality of the ground electrodesaligned linearly and spaced apart from the plurality of the activeelectrodes, and a plurality of the one or more temperature sensorspositioned at least partially under the plurality of the groundelectrodes.
 18. A method of applying thermal energy to tissue,comprising: inserting an expandable member having a plurality of pairsof electrodes within a patient; expanding the expandable member to anexpanded state; activating the plurality of electrode pairs; andmonitoring the temperature between the pairs of electrodes by measuringa temperature from each of one or more thermistors disposed between thepairs of electrodes.
 19. The method of claim 18, wherein at least one ofthe one or more thermistors is disposed between each pair of theplurality of pairs of electrodes, and further comprising monitoring thetemperature within each pair of electrodes by measuring a temperaturefrom at least one of the one or more thermistors disposed therebetween.20. The method of claim 18, wherein the pairs of electrodes are arrangedside-by-side and longitudinally along the expandable member, andinserting the expandable member is performed in an unexpanded state withthe expandable member folded at least between the pairs of electrodes.